Signal output circuits such as communication drivers used for in-vehicle communication, for example, perform slope control for the purpose of reducing radiation noise. In the slope control, the inclination of the rising and falling edges (hereinafter referred to as slope) of the output signal is controlled. A common technique of controlling the slope is to charge and discharge a capacitor and to use the terminal voltage of the capacitor to achieve a desired slope waveform.
With the capacitor connected between the drain and the gate of an output transistor having its drain connected to the output terminal of the signal, the apparent capacitance (hereinafter simply referred to as “capacitance”) when viewed from an input side is increased by the Miller effect. Accordingly, a desired slope waveform can be achieved using a capacitor that has a relatively small capacitance. With this configuration, however, if noise is superimposed on the output terminal, the noise may propagate to internal circuits through the capacitor and cause failures.
Patent Literature 1 discloses a technique of preventing such failures as mentioned above from occurring. In the configuration described in Patent Literature 1, an internal node that generates a slope-controlled signal is not connected to the output terminal that outputs the signal, and instead, the voltage of the internal node is made equal to the voltage of the output terminal by adding a current mirror circuit and the like. This configuration prevents failures when noise is superimposed on the output terminal, while achieving slope control of the output signal.